1. Field of the Invention
The present invention relates to a refrigerant and a refrigerating device, and in particular, to a flammable refrigerant in which an odorant is incorporated and a refrigerating device which utilizes the flammable refrigerant.
2. Description of the Related Art
Refrigerators and refrigerating devices for automatic vending machines and showcases have usually used, as a conventional refrigerant, chlorofluorocarbon refrigerants such as dichlorodifluoromethane (CFC-12), or hydrochlorofluorocarbon refrigerants such as chlorodifluoromethane (HCFC-12). When these refrigerants are released into the atmosphere and reach the ozone layer above the earth, the problem of destruction of the ozone layer arises. Thus, use of chlorofluorocarbon flon and hydrochlorofluorocarbon flon, which are refrigerants which have been used until now in refrigerating devices, has been prohibited or restricted.
As a result, hydrofluorocarbon refrigerants such as CH2FCF3 (HFC-134a) have been used as a substitute flon of the above refrigerants. However, even with such HFC refrigerants, a problem arises in that the effect thereof on global warming, which is another global environmental issue, is near the same level as that of the conventional HCFC-22 (CHCIF2) which is an HCFC refrigerant.
To solve such problems, hydrocarbon (HC) refrigerants such as propane and isobutane have recently been used as refrigerants for refrigerating devices. However, because the HC refrigerants are flammable, there is the possibility of spontaneous ignition or explosion when these refrigerants leak from a refrigerating circuit. Particularly, in the case of home refrigerators, since many heat sources often disposed near the home refrigerator, leakage of the flammable refrigerant may cause a major accident.
In view of the aforementioned facts, for refrigerating devices which utilize flammable gas refrigerants, it has been proposed to add odorants to refrigerants so that the leakage of the gas refrigerants can be detected. For example, Japanese Patent Application Laid-Open (JP-A) No. 8-14675 discloses addition of methylmercaptan, as an odorant made of sulfur-containing organic substance, to the HC refrigerant. However, methylmercaptan has high reactivity with copper, which is a material used in the refrigerating circuit, and changes (corrodes) the copper surface, which results in a shortened life of the copper. In addition, methylmercaptan also has high reactivity with refrigerating device oils. When it reacts with the refrigerating device oil, an insoluble reaction product will be generated in the refrigerant or in the refrigerating device oil, which insoluble reaction product may cause clogging of a capillary tube or the like in the refrigerating circuit after operation for a long period of time.
JP-A No. 8-245952 discloses that, in addition to mercaptane (methyl mercaptane, ethylmercaptane), dimethyl sulfide is added, as an odorant, to a flammable HFC refrigerant. However, dimethyl sulfide does not have an extremely strong offensive smell (it only has an onion-like smell), so that dimethyl sulfide alone does not sufficiently function as an odorant for the flammable refrigerant. As a result, it is generally used in combination with other odorants such as mercaptanes.
Therefore, a flammable refrigerant incorporating an odorant which odorant has no reactivity with copper, a material of the refrigerating circuit, or refrigerating device oils has not been developed.
An odorant is generally required to have such characteristics that it has an abnormal smell, is stable as a chemical substance, is non-toxic and harmless to humans, and the like. In addition, particular characteristics are required depending on materials to which the odorant is added. Therefore, a substance known as an odorant can not always be used as the odorant for other materials.
For example, tetrahydrothiophene (THT) has already been used as an odorant in combustion gases such as town gas (xe2x80x9cPerfumexe2x80x9d No. 146, June 1985). In addition to the above characteristics generally required for odorants, the following particular characteristics are necessary for odorants used in combustion gases: it burns safely and is odorless and harmless after combustion takes place, the odor is held in the gas so as not to be absorbed by gas pipes and meters, and the like. Because adding THT to combustion gases and adding THT in refrigerants for refrigerating circuit have been considered as two different things, use of THT in refrigerants has not been examined.
In view of the aforementioned facts, an object of the present invention is to provide a refrigerant in which an odorant is added, the odorant being compatible with refrigerants and refrigerating device oils, and having no reactivity with refrigerating device oils and materials used for refrigerating circuits, and to provide a refrigerating device in which the refrigerant is circulated in the refrigerating circuit.
The following refrigerants and refrigerating devices of the present invention are provided in order to achieve the above-described object.
A first aspect of the present invention is a refrigerant the main component of which is a hydrocarbon having 1 to 4 carbon atoms, or a flammable hydrocarbon fluoride derived by substituting one or more hydrogen atoms of the hydrocarbon with fluorine atoms, the refrigerant including a tetrahydrothiophene as an odorant.
A second aspect of the present invention is the refrigerant in which the amount of the odorant is in the range of 10 wt ppm to 0.5 wt %.
A third aspect of the present invention is the refrigerant in which purity of the hydrocarbon or the flammable hydrocarbon fluoride is at least 99.0 vol %, the content of unsaturated hydrocarbon is no more than 0.01 wt %, and the entire sulfur content is no more than 0.1 wt ppm.
A fourth aspect of the present invention is a refrigerating device in which the refrigerant of the first aspect of the invention is circulated in a refrigerating circuit in which a compressor, a heat releasing device, an expansion mechanism, and an evaporator are included.
A fifth aspect of the present invention is the refrigerating device in which a refrigerating device oil used in the compressor has a viscosity at 40xc2x0 C. of 5 to 300 cSt.
A sixth aspect of the present invention is the refrigerating device in which the refrigerating device oil includes a metal inactivating agent.
A seventh aspect of the present invention is the refrigerating device in which the refrigerating device oil includes one or more additives selected from the group consisting of moisture- and/or acid trapping agents, antioxidants, and extreme pressure additives.
An eighth aspect of the present invention is the refrigerating device in which residual oxygen in the refrigerating circuit is no more than 0.1 vol % of an internal capacity of the refrigerating circuit, and a residual moisture content in the refrigerating circuit is no more than 500 wt ppm with respect to a total of the refrigerant and the refrigerating device oil.
A ninth aspect of the present invention is the refrigerating device in which the refrigerating circuit is made of copper or copper alloy.
A tenth aspect of the present invention is the refrigerating device in which the refrigerating circuit further includes a drying device.
An eleventh aspect of the present invention is the refrigerating device in which the drying device contains a synthetic zeolite whose effective diameter falls in the range of 3 to 6 xc3x85.